My son was a D1-level swimmer who ultimately turned down at least one Ivy, William & Mary, and others for a top NESCAC. My sense is that the pre-med route would be tough to juggle along with varsity swimming. D1 swimming – even at an Ivy – is a very intense commitment. I would also say that, at least from our experience, DS is getting a truly first-rate education with small class sizes and talented teaching faculty. Those things are harder to find at D1.